Q: Good evening. I bought a magic mouse 2 days ago and it is recognized by the computer.

Good evening. I bought a magic mouse 2 days ago and it is recognized by the computer.

But, if I turn off this magic mouse ang if I turn on again, impossible to be recognized by the computer.

I'm obliged to use the trackpad and to go to "Preferences systeme" in order to identify again the magic mouse;

Let's suppose that I don't have a  trackpad and I'm obliged to change the batteries, it would be impossible to start again.

Certainly, I gorgot something, but which is the problem ?

OSX 10.11.3